docs: add a note that subgraph recreates indexes (#1404)

* docs: add a note that subgraph recreates indexes

* Update src/digraph.rs

---------

Co-authored-by: Ivan Carvalho <[email protected]>

Author: alessio-locatelli

src/digraph.rs

@@ -3003,7 +3003,8 @@ impl PyDiGraph {
     ///     It is worth noting that node and edge weight/data payloads are
     ///     passed by reference so if you update (not replace) an object used
     ///     as the weight in graph or the subgraph it will also be updated in
-    ///     the other.
+    ///     the other. Node and edge the indices will be recreated for the subgraph for compactness.
+    ///     Therefore, do not access data using the original graph's indices.
     /// :rtype: PyGraph
     ///
     #[pyo3(signature=(nodes, preserve_attrs=false),text_signature = "(self, nodes, /, preserve_attrs=False)")]